5.1.7

Energy and Ecosystems

5.1.7.1

Revise GCSE knowledge of Ecosystems and the Environment

Define terms used and give examples

Ecosystems

A distinct, self- supporting system of organisms interacting with each other and with a physical environment.

They can be large or small They encompass a range of habitats

They usually contain producers, consumers, decomposers and a physical environment

For each term give a definition and

two examples

Producer, Consumer, Decomposer,

Environment, Habitat

Definitions

A population is the sum total of all the organisms of a particular species found in an ecosystem at any one time

The population of all species is known as the community in that ecosystem

The ecological niche of an organism is the role of the organism in a community in terms of its habitat and interactions with other organisms. A given niche may be occupied by different organisms in different ecosystems

Pg 100 question 3

Food webs/ food chains

Food chains are the simplest way of showing feeding relationships

Grass Rabbit Fox The arrow shows the direction of energy flow

through the system Each stage in a food chain is known as a tropic

level. Food chains are an oversimplification, food

webs can give a fuller understanding

What are the benefits and downsides of showing feeding relationships as

Chains Webs

Pyramids of number

These represent the total numbers of organisms at each tropic level at a moment in time. It is irrespective of mass

Grass

RabbitsFoxes

Oak treeAphid

Ladybird

Pyramids of biomass

These represent the total biomass of organisms at each tropic level at a moment in time. It is irrespective of numbers

Biomass Number

Aphid

Ladybird

Oak tree

Questions

Question 3 pg 172

Ecology workbooks

5.1.7.2

Explain how energy is transferred between tropic levels

Calculate and explain efficiency of transfer

Energy transfer- Key processes

Photosynthesis fixes light energy into bonds between organic molecules

Respiration releases energy from organic molecules to make ATP which can ‘drive’ other processes

Synthesis of molecules and cells uses energy which can be passed to the next tropic level

Biological processes which use energy

Innefficiency and energy

Only 3% of sunlight is converted to chemical energy– Some light entirely misses leaves– Some light is reflected– Some light passes through– Only certain wavelengths are absorbed– Loss when transferred from chlorophyll to organic

molecules

Energy losses cont

Plants use about half of the energy they fix themselves– Energy is used during respiration for processes like

active transport

What is left can be passed to the next tropic level, but again there are losses– Not all parts of plant available to be eaten– Not everything eaten can be digested– Energy losses within consumers digestive system

Energy in ecosystems

Three things can happen to the energy taken in by organisms at a tropic level– Passed onto biomass of next tropic level when

eaten– Stored in detritus, passed onto decomposers when

the detritus decays– Converted to heat energy by inefficient chemical

reactions, radiated by warm bodies, or in friction due to movement. Heat energy is lost into the environment and cannot be regained by living organisms

Flow of energy

Eventually all the energy is lost to the environment as heat

Pyramids of energy

Pyramids of energy show how much energy is passed between tropic levels. They are always pyramidal (energy cannot be created)

The steep sides show the energy transfer is very inefficient- a lot is lost as heat

May have units- KJ m-2y-1

Shows energy transfer in a given area over a given time period.

Questions

Pg 100 question 1 & 2 Exam questions.

Homework

Using one, named, ecosystem produce a presentation illustrations what we have covered in the last two lessons.– Definitions and examples– Pyramids of number, biomass, energy– Energy flow (including ways of calculating)